Imagewise hardening direct-writing photodeveloped silver halide emulsion

ABSTRACT

A DIRECT WRITING SILVER HALIDE EMULSION IN AN UNHARDENED COLLOID BINDER CONTAINING A TANNING DEVELOPING AGENT PROVIDES ADVANTAGEOUS INTENSIFICATION AND STABILIZATION OF A PHOTODEVELOPED IMAGE. A PROCESS OF STABILIZING DIRECT WRITING IMAGES COMPRISING DEVELOPING AN UNHARDENED DIRECT WRITING EMULSION AFTER IMAGEWISE EXPOSURE AND PHOTODEVELOPMENT IN THE PRESENCE OF AT LEAST ONE TANNING DEVELOPER, FOLLOWED BY WASHING WITH HOT WATER.

United States Patent 3,671,245 IMAGEWISE HARDENING DIRECT-WRITING PHOTODEVELOPED SILVER HALIDE EMUL- SION Glenn Duane Stone, South Amboy, N.J., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del. No Drawing. Filed Nov. 24, 1969, Ser. No. 879,555

Int. Cl. G03c 5/24 U.S. CI. 96-64 5 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This invention relates to radiation-sensitive elements, and in particular to light-developable, direct-writing, radiation-sensitive elements of high speed and providing improved images and background stability. The invention also relates to a process for developing the elements and stabilizing the images.

The preparation and use of light-developable, directwriting, radiation-sensitive elements is well known. Because of image fading and background instability under extended periods of exposure to ambient light, it is desirable to process the image chemically for permanent reten'tion thereof.

Improved types of light-developable, direct-writing, radiation-sensitive elements are disclosed and claimed in assignees Hunt U.S. Pats. 3,033,678 and 3,033,682, May 8, 1962. These patents disclose and claim elements comprising direct writing silver halide emulsions having an average grain size in the range 0.1 to 10,microns and containing between 0.5 and 120 mole percent of a stannous salt based on the silver halide and preferably 5-40 mole percent. Such elements possess greatly increased writing. speeds and more readily stabilized background densities. By admixing plumbous salts with such emulsions during their preparation, as disclosed in Bigelow U.S.P. 3,178,293, Apr. 13, 1965, additional improvements'result.

A further improvement in the direct-writing art is set out in Hunt U.S. Pat. 3,249,440, May 3, 1966, where the silver halide emulsion layers contain molecular iodine. These layers have good direct-writing speeds and improved sensitometric characteristics as compared with the prior art.

Assignees Sincius U.S. application 645,601, June 13, 1967, discloses and claims an improved light-developable, direct writing silver halide emulsion sensitized with gold and iodine compounds. r Y

While the photosensitive elements set out in the above patents otfer -many-improvements in terms of higher writing speed, image and background stability, they are not entirely satisfactory, e.g., under the illumination of normal room light, background density continues to develop to a point where the image record is not sufiiciently clear. The image density also has the tendency to regress which is undesirable. These changes occur over a period of days of exposure to normal illumination. A further disadvantage of the elements is their instability, when exposed to higher intensity ultra-violet radiation or other radiation more intense than normal room lighting. This is a serious drawback as it does not permit reproduction of these records without ruining the original.

In the past most operators have wet-processed these direct writing elements when they desired to retain the records permanently or to use the record to make duplicate records by a photographic process. Although the more recent elements can use a conventional photographic developer to provide a high contrast black and white image of a permanent nature, a photographic fixing solution is still required.

Imagewise hardening of conventional, non-photodevelopable silver halide emulsions by tanning development is old, but the imagewise hardening of a visible photodeveloped direct writing silver halide emulsion is new.

SUMMARY OF THE INVENTION An object of this invention is to provide novel and improved emulsions, emulsion layers and elements. A further object is to provide a photodevelopable, direct-writing, radiation-sensitive element which has superior sensitometric characteristics in terms of maximum density and image stability. Another object is to provide a photodevelopable, direct-writing, radiation-sensitive silver halide element which can provide a relief image.

The radiation-sensitive elements of this invention comprise a photodevelopable, direct-writing, silver halide emulsion having an unhardened macromolecular waterpermeable, organic colloid binder containing a tanning developing agent. The processes of this invention provide a method of stabilizing and intensifying a direct writing image which comprises developing an unhardened photodevelopable, direct-writing emulsion, after imagewise exposure, e.g., in an oscillograph in the presence of at least one tanning developer, followed by washing with water at l40-180 F. This method is also shown to be useful when the image is photolyzed prior to the development.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 'The light-developable, direct-writing, light-sensitive emulsions used in the processes of this invention comprise an emulsion or dispersion of radiation-sensitive silver halide grains having an average grain size in the range 0.1 to 10 microns in a water-permeable macromolecular colloid having protective colloid properties for silver halide grains. In addition to admixing sensitizers and halogen acceptors, the emulsion is treated with a tanning developing agent. This agent may be carried in the emulsion, or in a separate bath. The binder used for the emulsion must have a chemical composition which is capable of harden ing, and similarly, should be soluble in hot water. Suitable such binders are gelatin and polyvinyl alcohol. Mixtures of gelatin with dextrin, and dextran and other colloids are useful.

The silver halide emulsions used in this invention are preferably of the silver bromide, or silver chlorobromide type, but other types, e.g. chloride, iodobromide can be.

used. Photodevelopable, light-sensitive emulsions useful in the processes of this invention are set forth in assignees Hunt U.S. Pat. 3,249,440 or Sincius application Ser. No. 645,601 filed June 13, 1967. Also Kitze U.S. Pat. 3,24l,-

exposure to actinic radiation for a short periqd there;

after. The element is then photodeveloped in room light for approximately 20-40 minutes, and the resulting imaged element treated in a high pH activator solution. After hardening, the background is washed off by a high impact hot water spray. The resulting image is of much higher contrast than the photodeveloped image, and is black against a white background.

The hardened image forms a relief which is suitable for use in imbibition printing, or as a photoresist.

The element is prepared by coating the photodevelopable emulsion on a suitable support, e.g., paper or an organic polymer film, e.g., polyethylene terephthalate, and drying to yield a dry coating Weight equivalent to about 30 mg. AgBr/dmfi. Suitable supports are listed in the patents cited above.

Between 15 and 120 mole percent per mole of silver of a suitable tanning developing agent is added to the emulsion prior to coating. Catechol, hydroquinone, spire-bis indanes, or alkyl gallates, where alkyl is 3-10 carbons, e.g., propyl gallate, are suitable tanning developing agents for use with the elements of this invention. Suitable spirobis indanes are described in Moede, U.S. 3,440,049.

An alternative embodiment of this invention provides for processing of a photodevelopable, direct-writing emulsion after imagewise exposure and photodevelopment in a tanning developer.

The following examples will better illustrate this invention, however, they are not intended to limit the scope thereof.

Example I A gelatino-silver halide emulsion was prepared by slowly adding an aqueous solution containing a mixture of 1 mole of silver nitrate and 0.033 mole of plumbous nitrate to an aqueous gelatin solution containing 1 mole of potassium chloride and acidified with 0.05 mole of hydrochloric acid. The precipitation was carried out under a red safelight. The temperature at precipitation and for 40 minutes thereafter was held at 160 F. An aqueous solution of 1.6 moles of KBr was added while the mixture was held at 160 F. The resulting emulsion was coagulated, washed, and redispersed in the manner described in Example I of Moede U.S. 2,772,165.

A solution of 4 grams of molecular iodine in 100 ml. of ethanol was added in an amount to provide a concentration of 1 mole percent iodine based on the silver halide. A suflicient amount of an aqueous'acidic gold chloride solution was added to provide 0.05 mole percent of gold (Au+++) based on the silver halide.

Coating aids were then added to the emulsion, and the emulsion coated on a light weight, non-hardening baryta coated paper support to give a dry coating weight equal to 30 mg. AgBr/dmF. The coated emulsion was dried in a conventional manner. I

Sample strips of the coating were exposed for 10- seconds through a 2l-step, /2 wedge of a sensitometer (Edgerton, Germeschausen and Grier Mauk VI). The

sample was held in darkness for 5 minutes, and then light- SOLUTION A j G. N-methyl-p-aminophenol sulfate and- 1 Hydroquinone Sodium meta bisulfite- 10 Water to make 1 liter;

- Followed by a 2 minute treatment in activator solution B. y

* SOLUTION B Sodium carbonate-100 g.

Water to make 1 liter.

, v. .The processed element was washed in l ot water (140 Number of [2 steps D H: Dnn visible N of; processed 0. 64 0.26 20 Processed 1. 07 0. 11 16 Any of the developer solutions described in US. Pat. 3,178,298 or 3,249,440 can be used instead of the above silver halide developers. i

I v I Example 11 The coated element prepared in Example I was exposed to an oscillograph trace at 80 inches per second, and held overnight in darkness prior to photodevelopment by irradiation from a white fluorescent lamp at an intensity of 30 foot-candles for 5 minutes.

The light developed strips were then treated for 5 minutes at 68 F. in the following developer solution.

Water liters 1- N-methyl-p-aminophenol sulfate g 5 Hydroquinone g 3 Sodium carbonate g 100 Sodium hydroxide to make pH 11.5.

All processed sheets were then washed in 140 F. hot water spray for 15 minutes, and dried in a conventional manner. i

A high contrast black on white image was obtained, which was stable when given lengthy exposures to actinic radiation.

' Example III A coated element prepared as in Example -I was exposed to a photographic halftone negative on a sensitometer (E.G. & G. Mark VII) for 10-4 seconds. The strip was held in darkness for 5 minutesand then photodeveloped as in Example II. r

The photodeveloped strips were treated in Solution A as prepared in Example I for 5 minutes, and then for 4.5 minutes insolution B which was prepared as set out in Example I, but with 100 ml. of solution A added thereto. All solutions at 70 F.

After washing in hot water as in Example II for 5 mins, a hardened high contrast black on white halftone image of archival quality was obtained. The image was stable upon long exposures to actinic radiation. The following table indicates that superior images were obtained after 1 processing.

Number of 112 steps DMax. DFog visible N 0t processed 0. 52 0. 23 20 Processed 1. 10 0.11 8

Example IV -A gelatino silver halide'emulsion was prepared as in:

' used in the'redispersed emulsion.

Example I'except'that, 0.15 of the amount of emulsion was used ascompared to Example I. 19 ml. of 4% iodine (4 gms. dissolved in ml. of ethanol), and 50 ml. of gold chloride (23 mg. dissolved in water with HCl), was

-This unhardened emulsion was coated, exposed, held, and photodeveloped as in Example I, with the exception that this emulsion was coated on a light weight non-hardening paper support having no baryta coating.

The photodeveloped image was treated for 2 minutes in the following one bath developer (described by Kerenson and Wells-British Journal of Photography, p. 4, January G. Hydroquinone 4 Sodium sulfite 2 Sodium carbonate 16 Potassium bromide 1 Water to make 1 liter.

N umber of [5 steps DMaX. DFoz visible Not processed 0. 70 0.30 19 Processed 1. O8 0. 18 18 Example V A gelatino silver halide emulsion was prepared and redispersed as in Example I, except that only 0.45 the amount was prepared.

After redispersion the emulsion was split into three equal portions.

Into the first portion A, was added 1 gm. of potassium iodide in 10 ml. distilled water. Then 50 ml. of gold chloride (as in Example IV), 5 ml. of 10% saponin, 5 gm. hydroquinone and 0.42 gm. sodium meta bisulfite in 125 ml. distilled water. pH was brought to 4.5 by addition of HCl.

To another portion B was added the following:

0.25 gm. potassium iodide dissolved in water to make 3 ml., 0.3 gm. potassium thiocyanate in 3 ml. distilled water, saponin as in portion A, 5 gm. hydroquinone and 0.2 gm. sodium meta bisulfite in 125 ml. distilled water. pH 4.5 established by addition of HCl.

To portion C was added 10 ml. distilled water, 0.05 gm. sodium carbonate monohydrate, then 0.1 gm. thiomalic acid. Hydroquinone, saponin, and pH were as in portion B.

Each portion was coated as in Example 1V. Each strip was exposed as in Example I, then light developed for min. at 30 foot candles intensity, and processed in a solution of 2 gm. sodium sulfite, 32 g. Na CO 10 gm. NaOH, 1 g. KBr, water to make 1 liter.

Dried samples revealed that tanning development was more complete in the imaged areas, however, thiomalic acid did not function as well in this application as the other halogen acceptors.

A gelatino silver halide emulsion was prepared as in Example I, but only 0.45 the total amount used in Example I was prepared, and the following halogen acceptors were used in different coatings, instead of the gold and iodine used in Example I.

(A) 0.3 gm. potassium thiocyanate in -3 ml. water, and 0.25 gm. potassium iodide in water to make 3 ml.

(B) As above (A) except potassium thiocyanate in 15 ml. distilled water, 0.1 gm. sodium carbonate monohydrate and .15 gm. thiomalic acid.

(C) As above, but no potassium iodide.

These samples were coated and exposed as in Example I. Processing was similar to Example I except that the activator solution contained gms. of sodium carbonate monohydrate, and samples were processed for 5 mins. in the developer and 7 mins. in the activator. High quality black on white images were produced. The following tables indicate that superior images were obtained in processed samples.

Number of 4 2 step DM Dru; visible 0. 70 0. 33 16 O. 79 0. 13 11 0.42 0. 21 14 8'2 2 O. 1 Thmmahc acld "{Processed 0. 60 0. 10 5 Example VII A gelatino silver halide emulsion was prepared as in Example I but only 0.45 the amount used in Example I was prepared, and redispersed as set forth in Moede US. 2,772,165, Example I. This emulsion was divided into 3 equal portions, labeled A, B, and C, to which the following were added.

To portion A. 0.05 gm. sodium carbonate (monohydrate) and 0.1 gm. thiomalic acid in 10 ml. distilled water. To portion B. 1 gm. potassium iodide in 10 ml. distilled water, and 0.23 gm. gold chloride dissolved in 50 ml.

distilled water with hydrochloric acid.

To both A and B there was added 1 gm. of 3,3,3,3'- tetramethyl-5,6,5',6-tetrahydrospiro-bis-indane in 40 ml. of 2 methoxyethanol, 1.7 gm. propyl gallate dissolved in 20 ml. methanol, and saponin as in Example IV. A pH of 4.5 was established with HCl.

To portion C. Potassium iodide and gold chloride were added as in portion B, also 5 gm. catechol and 0.4 gm. sodium meta bisulfite in 50 ml. distilled water; Saponin was added and pH adjusted as in B.

The emulsions were coated on a non hardening, non baryta coated paper support to a dry coating weight of 30 mg. AgBr/dmfi.

Each emulsion sample was exposed as in Example I and processed as follows:

Emulsion (A): 15 mins. photolysis at 40 footcandles intensity and then processed for 1 minute in a solution of 15 grns. NaOHI/liter of water.

Emulsion (B): Process for 1 min. in a solution of 5 gm. sodium bisulfite/liter; then photolysis for 10 mins. at 40 footcandles; then 3 mins. in a solution of 10 gm. Na CO /liter of water.

Emulsion (C): 5 minutes photolysis at 40 footcandles intensity, and then processed for 5 minutes in a solution of 10 gms. Na CO /liter of water.

Drying was done by conventional means, and all three samples yielded black on white images of good quality. The images were stable after 48 hours exposure to fluorescent room light.

The following tables indicate that superior images were obtained in processed samples.

' Number of [2 Steps 1 D MB! D Mm visible {Not processed 0. 59. 0. 24 16 (A) "lPr0cessed o. 84 0.15 12 B {Not processed 0. 64 0 2A 16 ProcessecL- 0. 81 0 16 7 {Not processe 0. 78 0. 51 19 Proeessed 0.86 0.07 12 The embodiments of the invention in which an exelusive property or privilege is claimed are defined as follows:

1. An image-forming process comprising l) imagewise exposing a layer of a photode'velopable,

direct-writing, silver halide dispersion in an unhardened water-permeable 'macromolecnlar organic colloid;

(2) photodeveloping the exposedlayer;

(3) developing the resulting layer in the presence of at least one tanning developing agent; "511d i I (4) removing the nonimaged areas of the layer by washing. 21

T 2. A process according to claim 1 wherein said layer contains a tanning developing agent.

- 3. A proce'ss according to claim 2 wherein said tanning developing agent is selected from the group consisting of catechol, hydroquinone and propyl gallate;

4. A process according to claim 1, wherein the colloid is gelatin.

5. A process according to claim 4, wherein the water has a temperature of 140180 F.

References Cited UNITED STATES PATENTS 8/1964 Yackel et a1 963.5,X

NORMAN G. TORCHIN, Primary Examiner 20 -W. H. LOUIE, JR., Assistant Examiner 11/1966 McBride 96-108 

